Alan Blumlein: Inventing Stereo Sound

(This is an archived post from our old blog.)

Alan Blumlein invented a lot of things. Here's a list of his patents. from Dora Media Productions' website where there's also information about Robert Charles Alexander's excellent book about Alan Blumlein.

The book is titled The Inventor of Stereo/The Life and Works of Alan Dower Blumlein and you can order it here.

Alan Blumlein had a lot to do with the fact that most home hifi setups have two speakers. The story goes something like: Alan takes his wife to a movie where he puts together the idea that the sound should follow the actors across the screen. Alan called the idea "Binaural Sound". (We now think of "binaural sound" as a recording specially recorded for listening through headphones... I believe Western Electric coined the term "stereophonic".)

Alan Blumlein described a method of recording sound using two microphones with figure-of-eight patterns arranged at 90 degree angles and a method of playing back the resulting audio using two loudspeakers. If Mr. Blumlein were alive today, I would ask him if he intended for recordings made with the Blumlein Technique to be played back with the speakers placed 90 degrees to each other.

Here's a nice description of how the mics are set up with Blumlein Technique.

According to Chesky Records, all of their recordings are made using Blumlein Technique.

In the early days of stereo recording, some engineers (possibly including Harvey Fletcher at Bell Labs) favored three-channel recordings, but I would guess the eventual dominance of the phonograph record pushed things to favor two-channel recordings.

Here's the Patent Specification for Blumlein's directional sound recording technique (also from Dora Music's excellent webpage.) Note that it's from 1931!

Alan Blumlein also did significant work at EMI on H2S Radar. Sadly, Alan Blumlein was killed in the crash of a Handley Page Halifax aircraft (pictured below) that was involved in H2S Radar tests.



It's amazing that Blumlein was granted 128 patents, especially considering that he died just short of his fortieth birthday.

Richard Burwen and his 20,000-watt hifi system

(This is an archived post from our old blog.)


click image to enlarge

(photo from: Audio Magazine/scrounge.org)


click image to enlarge

(photo from Richard Burwen's website.)



Okay, this is pretty fascinating stuff.

I realize it's pretty far off-topic for our single driver speaker blog, but anyway...

Who is Richard Burwen?

Here's his bio.

Here's just a small blurb from his bio in case you skipped the link:

Dick got into a lot of really interesting projects. Among the more challenging projects were ultra-low drift chopper-stabilized DC data amplifiers, IC multipliers and function generators, magnetometers, and low-noise switching power amplifiers. He designed circuitry of the first transistorized blood cell counter, a seizure detector for epilepsy, photoelectric relays, high resolution CRT displays, early projection color TV, a military satellite spin detector, and magnetometers for ground use and aircraft. His spacecraft magnetometer circuits successfully measured the magnetic field of the moon from orbit.

The article about Richard Burwen's 20,000-watt hifi system comes from Wayne's Speaker Building Page. The article is excerpted from Audio magazine, April, 1976. pp. 44-56 and was written by Richard S. Burwen.


click image to enlarge

(photo from: Audio Magazine/scrounge.org)


Here's a blurb about Richard's 20,000-watt hifi system:

Each of the five speaker horns is 13 ft. deep and has about 64 sq. ft. of mouth area. [i.e. 8 foot x 8 foot] The horns are conical, in preference to exponential, in order to produce a gradual low frequency rolloff, instead of a sharp cutoff. As it turned out, due to reinforcement from the room, the average low frequency response on one third octave bands is flat down to 16 Hz without equalization.

Each speaker horn contains 30 Cerwin-Vega tweeters, a midrange horn with two JBL 2440 drivers, and two Empire 16 in. woofers. In addition, the left-front and right-front horns have two 24 in. Cerwin-Vega woofers, mounted on the doors. These woofers are equipped with feedback windings to linearize their acoustic output over their range.

and...

To drive these speakers there are a total of 17 Phase Linear 400 amplifiers [200 watts RMS/channel @ 8 ohms].... Each woofer, midrange horn, and set of 9 or 12 tweeters is driven from one 200 watt amplifier channel. With the electronic crossover at 50, 400 and 5,000 Hz ahead of the amplifier, the speakers can produce the same sound level that would be produced by a single 20,000 watt amplifier.... The crossover filters utilize UM201 modules to produce 6-, 12-, 18-, and 30-db/octave cutoffs for the various drivers. In addition, the crossover provides equalization to lat acoustic response.


click image to enlarge

(photo from: Audio Magazine/scrounge.org)

Here's a great picture of Richard with his first hifi in 1945:


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(photo from Richard Burwen's website.)

...and here's his 2-watt amplifier with bass and treble controls, 1946.



click image to enlarge

(photo from Richard Burwen's website.)

You can follow this link to Richard Burwen's website. You'll notice that he's been keeping busy.

Astronomy Picture of the Day

(This is an archived post from our old blog.)




We've had the APOD link up for a while, but it's worth a more detailed mention.

The Astronomy Picture of the Day website
is "originated, written, coordinated, and edited since 1995 by Robert Nemiroff and Jerry Bonnell".

And just as the name promises, there's a new astronomy-related picture every day.

The APOD Archive is a great place to get lost when you're supposed to be working. They've been putting up a new picture every day since June of 1995 so there's a lot to see.

Here are links to the above photos:

Jupiter

Death Valley

Great fun.

Credits: Jupiter: NASA, Johns Hopkins U. APL, SWRI

Death Valley: Dan Duriscoe, U.S. National Park Service

Support Real Stereo

(This is an archived post from our old blog.)


The folks over at TNT-Audio have started the Campaign for Real Stereo.

I'll support that. I only have two ears.

(That doesn't mean I won't be perfectly happy to sell you five speakers!)

NASA's Gold Record

(This is an archived post from our old blog.)





Being a fan of LP records as well as spaceships, I've long been fascinated with the fact that the Voyager spacecraft have LP records on board, complete with instructions on how to play them.

But here's a recent article from the New York Times by Timothy Ferris who produced the LP.

He talks about how the record should last a billion years and how it almost didn't make it on board the spacecraft.

Really fascinating stuff.

(click image to enlarge)



There's Uranium 238 on the surface of the record so that someone, somewhere might be able to figure the age of the record.

Here's the Jet Propulsion Laboratory's official page on the Voyager record.

Jet Propulsion Lab's site also has some of the images that the disk contains.

It's a little eerie to look at the photos since we're sure to be cosmic dust by the time anyone finds the Voyager.

Cool.

Brutal Honesty in the Hi-Fi Business: Tim de Paravicini and tube warmth

(This is an archived post from our old blog.)

Hi-Fi. It's short for "High Fidelity". If fidelity means "the degree of exactness with which something is reproduced" (as the Oxford American Dictionary says) then wouldn't the best hi-fi system be one that plays back the recording as faithfully as possible?

Well, that's what we think. Once the music is recorded, we want the experience of listening to the recording to be as much like "being there" as possible. We don't want our hi-fi system to add "warmth" or "color" or anything else. We don't think The Philadelphia Story would be better in color and we don't think The Godfather would be better if we watched it through a sheet of gauze, so why would we want our hi-fi to "warm up" the recording?

...and since we feel this way, we thought we'd share a great quote that we came across in an interview of Tim de Paravicini of E.A.R. We don't know Tim de Paravicini and we don't sell his equipment. We just think it's a great quote.

interviewer: You use vacuum tubes in many of your designs. Some people have said that tubes have euphonic even-order harmonic distortion. Do you rely on this tube nonlinearity to achieve the sound of your mods, or do you always run the tubes in their linear region?

Tim de Paravicini: I do not rely on tube nonlinearity. I don't want a sound in my machines. What comes out must sound the same as what went in.

The "warmth" in a lot of tube electronics is due to their dismal top end, the bad transformers they use, and the loading down of their high-impedance outputs. Because of the output transformer and the feedback used, many tube circuits have a partial bass instability that gives a bloated bass. Any warmth in the tube sound is a defect, but listeners don't want to know that.

I don't have to use tubes in my designs; I only do it for marketing reasons. I've got an exact equivalent in solid state. I can make either type do the same job, and I have no preference. People can't pick which is which. And electrons have no memory of where they've been! The end result is what counts.

Our hats are off to Mr. de Paravicini. More people like this in the hi-fi business, please!

Here's the link to the entire interview over at E.A.R.

Avantone Mixcubes

(This is an archived post from our old blog.)


Let's say you've been reading up on single-driver speakers and are considering further investigation. Where do you start? If you go looking through the internet you'll likely discover a world of D.I.Y. speaker enclosures as tall as NBA players with drivers that are barely larger than a compact disc. Relax. All you wanna do is get your feet wet, right?

There's a little speaker called the Avantone Mixcube. I mentioned them in a previous post about the Auratone 5C. The Mixcubes are around $200 per pair. They're 93dB efficient so you can run them on just about anything.

The main thing is that we think they sound great. They really have that "single-driver musicality". This isn't a case of "spec a driver, slap it in a box and put your name on it". Ken Avant really worked with every aspect of this thing. And the presentation is great, too. A huge improvement over the Auratone 5C, with it's pasteboard/contact paper construction.

We know several people who have Best Buy-grade surround receivers who use Avantones with excellent results. They're great for movies and bring a terrific clarity to the dialogue.

I sometimes feel like we're shooting ourselves in the foot by recommending the Mixcubes. After all, we sell speakers that cost forty times as much. But really, they're like a "gateway drug". And in side-by-side comparisons, yes, the Tocaro 40s are worth the difference (shameless plugs abound!)

I'll warn you that there's a break-in time associated with the Mixcubes just so you don't get them out of the box and wonder what I'm talking about. During the first week or two of listening, they get a good deal better every day. This is not uncommon, in fact, I guess I don't really know of any loudspeaker that comes from the factory already broken in.

Did I mention that they have 1/4" Neoprene pads on the bottom? Or that they're shielded?

I can't recommend this little speaker enough. They're a bang-for-your-buck champ.

Here's the spec sheet from Avantone.